Glaucoma is the leading cause of irreversible blindness and affects more than 66 million people worldwide. The observations of abnormal mitochondrial respiration and down-regulation of mitochondrial fusion-related optic atrophy 1 (OPA1) gene expression in patients with primary open angle glaucoma suggest that mitochondrial dysfunction is as an important pathophysiological mechanism, contributing to glaucoma progression. We have identified that elevated intraocular pressure (IOP) triggers excessive mitochondrial fission and cristae depletion, as well as OPA1 gene deficiency in the retina and optic nerve head (ONH) of glaucomatous DBA/2J (D2) mice. Conversely, increased OPA1 expression promotes retinal ganglion cell (RGC) survival in D2 mice. Our preliminary results indicate elevated IOP impairs mitochondrial bioenergetics by reducing cellular ATP production and by increasing reactive oxygen species generation, as well as triggers formation of S-nitrosylation of the fission-promoting protein dynamin-related protein 1 (DRP1). More importantly, inhibition of DRP1 function by overexpression of dominant-negative DRP1 K38A mutant promotes RGC survival as well as preserves mitochondrial integrity in the ONH axons of glaucomatous D2 mice. The overall goal of this competitive renewal is to further characterize the pathophysiological consequences of altered mitochondrial dynamics (fission/fusion) and to assess their significance as therapeutic targets for protecting RGCs and its axons, as well as preserving structural integrity and synapses linking RGCs and the central visual pathway, and visual function in glaucoma. There are three specific aims: 1) To characterize the pathophysiological consequences of OPA1 deficiency or S-nitrosylation of DRP1 formation in RGCs. 2) To determine the protective effect of increasing OPA1 expression or inhibiting DRP1 function to ameliorate compromised mitochondrial integrity and bioenergetics in RGCs. 3) To determine whether increasing OPA1 expression or inhibiting DRP1 function can preserve the structural integrity and synapses linking RGCs and the central visual pathway, and visual function. This proposal will enhance our understanding of the pathophysiological mechanisms of mitochondrial dysfunction in glaucomatous neurodegeneration, and offer the scientific basis for identifying and developing new therapeutic strategies that could protect not only RGCs and their axons, but also the central visual pathway against glaucomatous damage.